1. Field of the Invention
The present invention relates to an optical mouse light emitter, and more particularly to a light emitter of an optical mouse that converges the light beams of its divergent light-emitting component into even parallel light beams.
2. Description of Related Art
A mouse is one of the necessary computer peripherals capable of moving a cursor freely on a screen. A rolling ball mouse has a ball situated in a base thereof, a circuit unit and a plurality of rollers disposed therein. As the rolling ball mouse is moved on a flat surface of a desk, the ball rolls on the surface to move the rollers, so that the circuit unit can compute the moving direction and displacement of the rolling ball mouse. However, the rolling ball picks up the dirt and dust on a surface easily, which will affect the mouse cursor movement. Therefore, a non-contact optical mouse that applies the optical sensing theory was introduced. An optical mouse has a light-emitting component, an optical mechanism, a sensor and a circuit unit therein. As the optical mouse is moved on a flat surface of a desk, light from the light-emitting component passes through a part of the optical mechanism and is focused on the flat surface of a desk. The light is diffused by the flat surface of a desk and reflected to another part of the optical mechanism, such that the light is focused at the sensor and the circuit unit can compute the moving direction and displacement of the optical mouse.
Reference is made to FIG. 1 of a prior-art optical mouse light emitter, which comprises a transparent body 4 and a divergent light-emitting component 5. The transparent body 4 has a front end surface 40 and a lateral circular surface 42. The light-emitting component 5 is disposed in the transparent body 4. The light L1 emitted from the light-emitting component 5 through the front end surface 40 of the transparent body 4 forms a light collection area A, and the light L2 emitted from the light-emitting component 5 through the lateral circular surface 42 of the transparent body 4 is diffused outside the light collection area A. In the foregoing prior-art optical mouse light emitter, the light L1 passing through the light collection area A and the light L2 diffused outside the light collection area A cannot form an even parallel light beam as the optical mouse is moved on a flat surface of a desk. The light of the light-emitting component 5 passing through a part of the optical mechanism of the optical mouse is focused at the flat surface of a desk, and the light is diffused by the flat surface and reflected to another part of the optical mechanism, such that the light is focused at the sensor of the optical mouse and the circuit unit of the optical mouse can compute the moving direction and displacement of the optical mouse. However, if the light passing through a part of the optical mechanism is focused at the flat surface of a desk, a light interference phenomenon will occur to produce uneven illumination and form bright rings and dark rings alternatingly aligned, which phenomenon is know as the airy disc.
Reference is made to FIG. 2. A point P originally falls in the region of a bright ring B. As the optical mouse is moved, the bright ring B and the dark ring D move accordingly, such that the point P falls in the region of a dark ring D. As a result, an unstable potential will be produced after the sensor receives the light, and that will cause a poor optical sensing effect or the optical mouse cursor cannot be moved smoothly on the screen. Furthermore, the light L2 emitted from the light-emitting component 5 through the lateral circular surface 42 of the transparent body 4 cannot be used. Illumination thereof is thus very low, which results in a poor optical sensing effect and a waste of the electric power consumption to the optical mouse.
In another prior-art optical mouse, the light-emitting component adopts a laser component instead of the foregoing divergent light-emitting component. Although the laser component does not have the light diffusion problem of the foregoing divergent light-emitting component, it is too expensive.